spatial variability of soil properties and irrigated wheat yield in a quantitative suitability map, a case study: shahr-e-kian area, chaharmahal-va-bakhtiari province

abstract the quality of soil maps depends upon their ability to show the soils variability. thus, the accuracy of the maps used for crop recommendations is due to the accuracy of soil maps. this study was performed to investigate the amount of soil properties and crop yield spatial variability in s 2 and s3 units of a semi-detailed quantitative suitability map (1:50000 scale) for irrigated wheat in shahr-e-kian area, chaharmahal-va-bakhtiari province. eighty soil samples were collected in each land unit at 0-30 cm depth using multi-scale sampling method to determine available p, k, total n, %o.m., %caco3 equivalent, soil texture and particle size distribution, ec and ph. a 0.5×0.5 m plot of wheat was harvested at each of 160 sites previously sampled to determine crop biomass, 1000 seeds weight and harvest index. the highest cv was related to available potassium (47.43 for s2 and 46.46 for s3 units, respectively) and the lowest one was related to ph (1.07 for s2 and 0.925 for s3 units, respectively). variography showed a good spatial structure for all variables in both land units. ranges for variograms were from 17.75 for n to 61.06 m for ec in s2 unit and from 17.47 for p to 62.93 m for 1000 seeds weight in s3 unit. kriging maps showed high spatial variability of soil properties as well as biomass, wheat yield and harvest index within two land units. this indicates that suitability maps have not enough credibility for precision agriculture. using information of all pedons as well as representative pedons in land units and combining the information of suitability maps with geostatistical data can be a choice way to improve the accuracy and quality of land suitability maps.